IBM 3745
COInInunication Controller
Product and Technology Overview
Enhanced technology and functional capability
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IDM3746
Expansion Unit
ModelLl4
IDM3746
Expansion Unit
ModelLl3
IBM 3745
Communication ControUer
Model 210 or 410
Lea~ teehnologyworking for you
IBM 3746
&ponsion Unil
MotlelA12
Improved performance
The latest generation within the
mM 37XX family of communication
controllers, the 3745 takes controller
technology a major stage forwards. The
basic 3745 model offers approximately
twice the performance of the mM 3725
Communication Controller, whilst
expansion options boost connectivity
and handling capacity.
In addition, new concepts in product
architecture and component relationships
have been incoIpOrated to improve the
standards of reliability, availability and
serviceability already demonstrated by
the 37XX family.
New levels of modularity
Modular construction allows users to
match connectivity requirements to their
needs, and at the same time provides a
simple pathway for future system growth
and expansion. Modularity also extends to
concurrent maintenance, providing the
benefits of online diagnostics and
component replacement For improved
versatility, 'hot pluggability' allOW8
selection of the configuration which best
mee~ current needs - without impacting
other'machine functions - 80 that users
can react quickly to changing
requirements.
This major advance in communication
controllers also reflects the increasing
8Ophistication of the mM product
development process itself. Improved
project tracking and even closer
co-operation between design and
manufacturing divi8ions have ensured
improved product quality, system
performance and availability.
New standards of performance at your command
The 3745 answers the three main
requirements identified in extensive
discussions with existing users of IBM
communication controllers; increased
availability, improved performance and
enhanced connectivity.
Once these objectives were defined, the
development of the 3745 was structured to
ensure that they would be attained.
Tracking methods were refined so that the
pathway to Engineering Verification Tests,
first of the important 3745 development
milestones, was achieved in a single pass
- eliminating the iterative steps normally
required for such a sophisticated product.
To increase availability, and at the
same time provide enhanced speed and
performance, provision has been made for
duplication of the Central Control Unit
(CCU), the 'engine' at the heart of the
3745. This allows operational flexibility
from full backup through to much
enhanced handling capability with two
CCUs operating simultaneously.
sixteen such lines, of which eight may be
active simultaneously.
traHic; and the channel adapters, which
provide the links to host computers.
To overcome the potential bottleneck of
normal input/ output transaction speeds,
Direct Memory Access (DMA) technology
bypasses the main 110 bus on the new
high-speed data channels. The maximum
capacity of the DMA bus is approximately
8 megabytes per second.
Four LIC types provide line attachment for
V24, V25, V35 and X2 1 interfaces, and the
scan ner 'incorporated in the 3745 is
designed for excellent performance over a
wide range of line speeds, from 50 bps to
256 kbps.
Better connectivity
Many design enhancements involve the
components directly concerned with
connectivity and data handling, namely
the Line Interface Couplers (LICs); the
scan ners which receive and direct data
In parallel with the improved processing
power of the 3745, host connectivity has
also been enhanced to include 16 channel
adapters. Tn block multiplexer mode, the
3745 channel adapters also support data
streaming, increasing both instantaneous
throughput and the maximum permissible
channel lengths to 400ft (120m).
In the interests of serviceability, the 3745
has been designed to facilitate both 'hot
pluggability' and concurrent maintenance.
To improve manageability, a fixed disk
provides the capacity to store multiple
load modules of the Network Control
Program (NCP).
Processing performance has been
enhanced by the use of advanced
Complementary Metal Oxide
Semiconductor (CMOS) technology in
many areas of the machine; high-speed
bipolar chips for many critical functions;
and by a new design for the CCU itself,
which now makes use of air-cooled
Thermal Conduction Module (TCM)
technology.
The dual Central Control Units of the
Model 410 provide complete fl exibility from
full backup to simultaneous operation
New high-speed data ports
Meeting the challenge of the latest
developments in telecommunications
networks, the 3745 offers greatly increased
overall line handling capacity, and can
also accommodate high-speed Tl and
2 Mbps lines. The 3745 is the first IBM
communication controller to provide a
unique scanner for Tl and 2 Mbps lines,
and has the capacity to handle up to
The impact of new technology and
improved packaging densities are evident
w hen comparing a 256 kilobyte card from
the 3725 with the smaller, 4 megabytes
capacity 3745 card
Performance comparison
The single or dual 3745 CCUs, each more
powerful than the single CCU of the 3725,
operate with a 75 nanosecond cycle time,
allowing the 3745 to process instructions
significantly faster than the 3725.
In addition to faster processors, Direct
Memory Access and design improvements
such as increased line capacity, high-speed
scanners, and cache memory mean that
the new 3745 achieves much better performance when compared with previous
IBM communication controllers.
Since communication controller
performance depends on line speeds,
protocols, message lengths and other
traffic characteristics, the graph opposite
has been prepared to illustrate the
comparative performance of 3745 models
with that of the 3725.
Installation flexibility
The IBM 3745 Communication Controller
is available in two models, the Model 210
with a single CCU, and the Model 410 with
dual CCUs. Initial choice does not limit
future expansion s, since the Model 210
may be fi eld upgraded.
TIaese cIrorts provide examp1es of
typicolperformance baled on the
number tf active connections which
can be 811pported by the 3725, 3745
MOOd 210 and 3745 Model 410for
selected line speeds and operating
environments. The 37251w.s been
assigned a value of 1, and 3745
perfOl"mlJ1&CeS are shown in. relation to
tIrol tfthe 3725. Thefirst set represents
an in.teracti.ve . . applicatWn,
whilst the
third represent
batch troJfic for Intermediate Network
Nodes (INN) to a Jwst applicatWn
seco-:::t::2i
1.0
Interactive tJaffic
9600 bps full duplex
Batch tJaffic
56000 bJlll full duplex
Batch tJaffic
1544000 bps half duplex
A 3745 Model 210 can be conn ected to
up to eight host computers. Also, up to
12810w/ medium speed lines, eight Tl or
2 Mbps lines, eight IBM Token-Ring
networks, or certain combinations of
these, can be supported. Optional
IBM 3746 Expansion Units provide
additional attachments for up to 16 hosts
and 512 lines.
The 3745 can handle up to 16 high-speed
T1 or 2 Mbps lines, using a new high-speed
scanner
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Building on a proven architecture
In developing the IBM 3745
Communication Controller, the challenge
was to improve on the highly successful
design of the 3725. This has been acrueved
by designing a package incorporating
new technology wruch is cost-effective,
occupies less floorspace and consumes less
power, yet wruch provides rugher overall
performance.
The most important change to the
arcrutecture and function of the 3745 is
dual CCU capability, each with its own 4 or
8 megabyte memory, and running its own
NCP. Mode switcrung via a bus switch can
provide either full or partial backup, and
while each CCU individually provides
higher capacity for extra line connectivity,
this is further enhanced if backup facilities
are not required and both CCUs are
operating simultaneously.
More efficient input/ output
To boost the efficiency of data transfer,
dual 110 buses per CCU reduce traffic
congestion on the links between 3745
components, when compared to the single
bus of the 3725. Data and instruction flow
between the CCU and scanners, and
between the CCU and channel adapters,
is rustributed over the two 110 buses.
However, performance would have
been inhibited if all rugh-speed scanner
traffic had to pass through the CCU; the
additional Direct Memory Access (DMA)
bus is the key to providing increased rughspeed line support. The DMA bus is a
rurect link between the rugh-speed
scanner and main memory for most
operations, thus freeing the CCU for
other function s.
To speed operations further, a cache
memory has been added to the arcrutecture to act as a rugh-speed buffer, allowing
the CCU to fetch and store commonly used
instructions and data from memory at CCU
speed, thus improving program execution
by reducing read/ write delays.
Distributed processing and power
supply
Microprocessors distributed throughout
the machine provide increased effi ciency
in task performance. These microprocessors run the independently
operating 'microcode', wruch controls
low-level fun ctions of scanners, channel
adapters, power blocks and other
components.
For ease of controller change and
growth, the 3745 also has components that
perform multiple fun ctions. Protocolindependent Line Interface Couplers
support a wide range of speeds, a single
scanner type supports line speeds from
50 bps to 256 khps, wrule channel adapters
support byte, block and selector
attachment.
Selective scanning is a further
enhancement in that the scanner in the
3745 scans only those LICs that have
activated lines. This means that users can
configure their system so that the scanner
can support different configurations at
various time periods. For example, the
same scanner can both support a large
daytime interactive appli cation and
handle a nightime batch traffic
application.
In addition to the distributed microprocessor architecture, a distributed power
system with individual power blocks for
each important component means that,
whichever configuration is selected,
electrical supply demands are matched to
the configuration.
This distributed power system enables the
3745 to offer concurrent maintenance,
wruch allows diagnostics to be run and
components to be replaced while the
controller remains operational.
3745 Ardlitecture
3725 Architecture
Schematic of3745 layout compared with
tlwtof3725
Technological advances harnessed in the IBM 3745
The 3745 has been designed throughout
using the latest IBM technology.
CCU
The Central ContTol Unit (CCU) of the
3725 consisted of ten cards mounted on
a logic board, and required complex
conn ection arrangements to ensure
that clocking variations were kept to a
minimum . In the 3745, the ten ca rds have
bee n reduced to a single air-cooled
module containing 104 high-speed chips,
resulting in a processor cycle time of
75 nanoseco nds. Advances in packaging
design have made possible this high
processor density, overcoming inter-chip
wiring delays and power dissipation
inequaliti es, and achieving gate delays
of I nanosecond and RAM access times
of less than 10 nanoseconds.
3745 CCU module compared with the
3725 CCU
TCM
The air-cooled Thermal Conduction
Module (TCM) houses and cools the 104
bipolar chips containing the processor
logic, cache memory and control storage,
mounted on the surface of a multilayer
substrate. The substrate is clamped
betwee n a base plate and a :hat' with
spring-loaded metal pistons. Each piston
presses against a chip, condu cting heat
to a heatsink bolted on top of the ' hat'.
The cooling system adopts the sa me
successful approach as that of the IBM
9370 Information System, the TCM giving
up the heat to ambient temperature air
passing over it by forced convection. As
part of the distributed microprocessor
subsystem, air flows are closely controlJed,
with automatic shutdown in the event that
temperatures ever exceed safe operating
limits.
Sealing Ring
One-megabit memory chip
Industry-leading IBM one-megabit chips
are used on the storage cards, expanding
available memory up to either 4 or 8
megabytes. These high-density memory
modules have increased resistance to 'soft'
errors caused by background radiation,
and special ~ogic error circuitry helps to
detect and correct failures.
lli?06CDll.A
3745 one-megabit chip compared with a
3725 memory card
CM OS technology
To increase packaging density, reduce
power consumption and enhance
processing power, CMOS gate array
technology has been used for much of the
CCU interface, direct memory access and
I/O bus switching functions. These gate
arrays offer ease of design and reduce
circuit delays, and can incorporate densities of up to 10,000 circuits per chip.
The low speed scanners use CMOS
technology for a majority of the logic
design , with bipolar chips to interface with
the memory. Use of high density CMOS
gate arrays, associated with 256 kilobit
memory chips, reduces a five card design
in the 3725 to two cards in the 3745.
The high-speed scanner uses the latest
IBM I-micron logic CMOS design, and is
one of the first IBM products to implement
this leading-edge technology, providing
a capacity of 40,000 standard cells per
module. These high density modules allow
much of the NCr buffer chaining functions to be integrated into the hardware
and thus support Tl and 2 Mbps line
performance.
The IBM 40,OOO-cell chip used in the highspeed scanner (actual su1ace is less than
1 cmsq.)
New features for improved operational control
The 3745 introduces an even higher
level of controller manageability than the
3725, via the enhanced Maintenance and
Operator Subsystem (MOSS). Menu
selection screens guide the operator
through tasks, eliminating many of the
indicators and switches of earlier
controllers.
Enhanced MOSS function
Many operations are carried out via
microcode, which distributes instructions
from storage to microprocessors throughout the 3745. These microprocessors not
only control power supply sequ encing, but
also many of the fun ctions form erly carried
out by service personnel, thu s providing
MOSS provides microprocessor-controlled considerable additional hardware
flexibility.
access to the 3745, from initial load, the
control of bus switching between CCUs,
This configuration fl exibility includes the
and the management of operational
modes, through to running of diagnostics, setting of direct attachment lin e speeds
from NCP. Tn addition , the setting of suband the recording and analysis of events.
channel addresses is a new fun ction
carri ed out by MOSS during mi croprogram
load and which can be moditied via the
MOSS console. Channel adapters can also
be enabled and disabled from the MOSS
console, instead of via switches at the
control panel. Another operational
feature, implemented via MOSS, is port
swapping, the ability to bypass a failing
controller port.
Altering LIe configurations is now a simple
online operation
TM NetView is a trademark of International Business
Machines Corporation.
Online changes
Tn addition, the 3745 has customeraccessible areas, allowing appropriate
customer personnel to carry out 'hot
pluggability' operations, to adap,t the
controller qui ckly and easily to network
change and growth. LICs, packaged in
protective cassettes, can be removed and
added with power on , without aHecting
even those U Cs supported by the sam e
scanner.
The IBM 3745 Communication Controller
is supported by NetVi ew rl', the IBM
integrated network management program.
Error information is provided to the host
network operator, who can use the information to identify the cause of network
problems, thu s providing improved
network control and increased availability
for end-users.
Enhanced design for better availability
Every new IBM product is required to
demonstrate that it has attained the
qualities of RAS (reliability, availability
and serviceability) appropriate to its
stature as the latest development in a given
field. This demanding design directive has
ensured that the 3745 not only offers
improved performance, but also eminence
in other equally important areas.
switches to LICs, scanners, channel
adapters and other components may be
selectively disabled, allowing safe
replacement.
The 3745 incorporates improved data
capture and analysis systems. Reports are
made to MOSS and can also be made
available to the optional Remote Support
Facility (RSF). The worldwide IBM
RETAIN database is used to identifY the
fault type, so that a local IBM Customer
Engineer can be despatched rapidly with
the appropriate replacement. If the
problem is in the microcode, highly
trained specialists can interrogate the 3745
remotely via telecommunications links
and MOSS to provide corrections, a facility
which also extends to communicating
known fixes to microcode problems.
Dual CCU modes
A primary 3745 feature for availability is
the provision of dual CCUs on the Model
410, which can operate in any of three
modes:
o Twin-in-standby mode, with only
one CCU active. Scanners and channel
adapters on a disrupted CCU can be
switched to the alternate CCU, either
manually or automatically.
o Twin-in-backup mode, in which a CCU
can take over all or part of the traffic of the
second CCu.
o Twin-in-dual mode, with both CCUs
operating independently to their full
capacity, handling the maximum volume
of traffic.
A 45-megabyte fixed disk makes a
significant contribution towards
availability, and also to the suitability of
the 3745 for remote and unattended site
installation. The Network Control
Program (NCP) may be downloaded
without disrupting network traffic and
held locally, ready to initiate a rapid restart
iJ required. The fixed disk can store two
load modules per CCU, together with a
dump of memory contents for later
analysis.
Improved controller management is
provided by enhancements to the
Maintenance and Operator Subsystem
(MOSS)
Improved fault handling
Other aspects of design also focus upon
availability. For example, since scanner
events are often temporary, caused by
unusual line traffic, the ability to
automatically reload microcode reduces
scanner outages. Diagnostics may be run
from MOSS, and the modular distributed
power supplies allow maintenance to be
performed concurrently with 3745
operation. Individual power onl off
Providing rapid solutions to customer
problems is the task of the highly trained
engineers of the Remote Support Facility
Achievement in manufacturing excellence
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mM 3745 Comnumication Controller Model
210 base unit - offering attachment capabilityfor up to eight host computers, as well
as up to 128 low/ medium speed lines, eight
T1 or 2 Mbps lines, eight IBM Token-Ring
networks, or certain combinations of these
In the development of the 3745,
manufacturing specialists have fonned
a pennanent part of the 3745 team right
from early concept stages. They were
therefore able to provide the benefits of
their experience with the 3725, and an
increased awareness of advances in
production techniques. The elimination
of potential sources of manufacturing
problems at the outset eased the transition
from development to manufacturing
phases, reducing the time to product
launch, and providing a further assurance
of the high quality of this product.
The scanner used in the 3745 supports all
line speeds from 50 bps to 256 kbps
The installation of the CCUI TCM module
demands highly skilled technicians
Installation of one of the many distributed
power supply blocks, which ensure
improved availability for the 3745
Assembly ofone of the 16 channel adapters
which provide host connectivity
Quality assurance is naturally at the heart
of the 3745 manufacturing process. Only
components of the highest quality have
been selected for use in the 3745, and
sophisticated tracking procedures have
been established to monitor component
perfonnance.
The manufacture of this worldwide IBM
product takes place in Raleigh in North
Carolina, USA; Havant in the UK; and
Fujisawa in Japan.
Improved efficiency
The 3745 production process makes use
of the advanced manufacturing concept
known as Continuous Flow
Manufacturing (CFM). CFM, taken
together with the high degree of early
manufacturing involvement with the
project, reduces manufacturing
complexity as well as the manufacturing
cycle time.
Automated test stations using IBM PC ATs
functionally test each completed
communication controller, and an IBM
computer-controlled system monitors
overall test data.
Yet, whilst technologically advanced
methods of production ensure optimum
efficiency in the process itself, the care and
attention to detail which have been
invested in the manufacture of the 3745
are the important factors in providing
users with the reassurance of improved
product quality and enhanced reliability.
Completed units are comprehensively
tested by purpose-designed diagnostic
software run on an IBM PC AT
The IBM 3745 - evolutionary a~vance in communication controller design
Based on the proven architecture of the
IBM 37XX controller family. the new
IBM 3745 Communication Controller has
been designed to provide the benefits of
higher performance and avaiJabiJif}'.
It incorporates features aimed at achieving
better serviceabilif}' and manageabilif}',
together with options for enhancement
and expansion to provide increased
flexibilif}' for future system growth and
change.
Through the use of new technology,
the 3745 also offers improved capabilities
in high-speed data handling. With the
capacif}' to cope with increasingly
demanding requirements for enhanced
connectivif}' and capacif}' in data
communication systems, the 3745 is a
major advance in communication
controllerdesign.
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In general, comparisons in this broch ure are made with the perfonnance and
characte ristics of the IB M 3725 Commu nication Controller and earlier
models.
Refe rences in thi s publication to IBM products, programs or servi ces do not
imply that IBM intend s to make these avail abl e in all countries in which IBM
operates. Any refere nce to an IBM lice nsed program in this publication is not
in te nded to state or imply that only IBM's licensed programs may be used.
Any functionally equivalent progra m may be used instead.
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